Gas seal for aerospace engines and the like

ABSTRACT

A gas seal for aerospace engines has a stationary seal housing, a rotating seal plate mounted on the engine drive shaft and a carbon ring seal movably supported in the housing with a face which mates with the face of the seal plate to create a gas seal therebetween. A plurality of flexible pins have first ends supported on the housing and second ends slidably connected with the carbon ring seal to permit the latter to shift axially. A plurality of compression springs bias the two seal faces together. The housing has a first twist lock which selectively engages a second twist lock on the carbon ring seal to movably retain the latter in the housing. The second ends of the spring pins resiliently deflect during mutual rotation of the carbon ring seal and the housing to facilitate engagement and disengagement of the first and second twist locks.

CLAIM OF PRIORITY

Applicants hereby claim the priority benefits under the provisions of 35U.S.C. §120 to related Provisional Patent Application Ser. No.61/143,984, filed Jan. 12, 2009 on AEROSPACE LIFT OFF SEAL.

BACKGROUND OF THE INVENTION

The present invention relates to gas seals, and in particular to a gasseal for aerospace engines and other similar applications.

Gas seals are generally well known in the art, and are used inconjunction with a wide variety of turbo machinery, such as jet engines,turbines, compressors and the like, to form a non-liquid or gas sealbetween two portions of an associated turbo machine Examples of such gasseals are disclosed in U.S. Pat. Nos. 3,640,541; 5,066,026; 5,174,584and 6,142,728. In general, such gas seals include a rotating metal sealplate that is attached to an associated rotating drive shaft, whichincorporates an annular face that seals against the annular face of anassociated stationary face seal or ring that is typically made of carbonor the like and mounted in an associated stationary housing. A biasingmechanism, such as springs or the like, is typically provided to urgeadjacent faces of the carbon ring seal and the seal plate together.Furthermore, in non-contacting or lift off gas seals, the interior orsealing face of the carbon ring seal is typically provided with a seriesof very small grooves which form gas ramps that hydrodynamically createa thin gas film between the adjacent faces of the carbon ring seal andthe seal plate, such that the same lift off of one another and do notactually come into contact when the gas seal is in full operation.

Gas seals for aerospace engines must be extremely lightweight, compact,capable of withstanding very high pressures and temperatures, and verydurable even at extremely high speeds in excess of 26,000 rpm. A gasseal which can meet the exacting dimensional, weight, stress and thermaldemands experienced in high speed aircraft gas turbine engines would beclearly advantageous.

SUMMARY OF THE INVENTION

One aspect of the present invention is a gas seal for aerospace enginesand the like of the type having an engine housing with an engine driveshaft rotatably mounted therein. A stationary seal housing is configuredfor rigid connection with the engine housing. A rotating seal plate isconfigured for operable connection with the engine drive shaft, rotatestherewith relative to the seal housing and has a seal face. A carbonring seal is supported in the seal housing and includes a seal facewhich mates with the seal face of the seal plate to create a gas sealbetween the engine housing and the engine drive shaft. A plurality offlexible spring pins have first ends thereof supported on the sealhousing and second ends thereof slidingly connected with the carbon ringseal to permit the carbon ring seal to selectively shift axially in theseal housing toward and away from the seal plate. A plurality ofcompression springs are supported on the flexible spring pins and biasthe seal face of the carbon ring seal axially into a sealingrelationship with the seal face of the seal plate. A first twist lockmember is associated with the seal housing, and a second twist lockmember is associated with the carbon ring seal and is configured to matewith the first twist lock member associated with the seal housing tosecurely yet detachably retain the carbon ring seal in the seal housing.The second ends of the flexible spring pins are laterally flexiblerelative to the first ends of the flexible spring pins, and canresiliently deflect in a generally circular fashion during mutualrotation of the seal housing and the carbon ring seal to facilitateengagement and disengagement of the first and second twist lock members.

Another aspect of the present invention is a gas seal for aerospaceengines and the like of the type having an engine housing with an enginedrive shaft rotatably mounted therein. A stationary seal housing isconfigured for rigid connection with the engine housing. A rotating sealplate is configured for operable connection with the engine drive shaft,rotates therewith relative to the seal housing and has a seal face. Acarbon ring seal is moveably supported in the seal housing and includesa seal face which mates with the seal face of the seal plate to create agas seal between the engine housing and the engine drive shaft. Aplurality of pins have first ends thereof supported on the seal housingand second ends thereof slidingly connected with the carbon ring seal topermit the carbon ring seal to selectively shift axially in the sealhousing toward and away from the seal plate. A plurality of compressionsprings bias the seal face of the carbon ring seal axially into asealing relationship with the seal face of the seal plate. The sealhousing has an outer side adapted for communication with a relative highpressure portion of the engine housing, and an inner side adapted forcommunication with a relatively low pressure portion of the enginehousing. A first passageway is positioned in the seal housing, such thatradially interior portions of the seal faces of the seal plate and thecarbon ring seal communicate with the high pressure portion of theengine housing, and radially exterior portions of the seal faces of theseal plate and the carbon ring seal communicate with the lower pressureportion of the engine housing. A second passageway in the seal housingcommunicates the high pressure portion of the engine housing with anexterior face of the carbon ring seal to urge the seal face of thecarbon ring seal toward the seal face of the seal plate. The seal facesof seal plate and the carbon ring seal are configured to create adynamic gas film therebetween during operation from the controlled flowof gas from the high pressure portion of the engine housing to the lowpressure portion of the engine housing. A locking plate is configuredfor operable connection with the engine drive shaft and rotatestherewith along with the seal plate relative to the seal housing. Thelocking plate movably supports the seal plate to permit the seal plateto shift axially toward and away from the carbon ring seal. A pressurebalance plate is configured for operable connection with the enginedrive shaft and rotates therewith along with the seal plate relative tothe seal housing. The pressure balance plate includes an annular groovedisposed along an inside face of the seal plate which communicates withthe high pressure portion of the engine compartment to urge the sealface of the seal plate toward the seal face of the carbon ring seal.

Yet another aspect of the present invention is a gas seal for aerospaceengines and the like of the type having an engine housing with an enginedrive shaft rotatably mounted therein. A stationary seal housing isconfigured for rigid connection with the engine housing. A rotating sealplate is configured for operable connection with the engine drive shaft,rotates therewith relative to the seal housing and has a seal face. Acarbon ring seal is moveably supported in the seal housing and includesa seal face which mates with the seal face of the seal plate to create agas seal between the engine housing and the engine drive shaft. Aplurality of pins have first ends thereof supported on the seal housingand second ends thereof slidingly connected with the carbon ring seal topermit the carbon ring seal to selectively shift axially in the sealhousing toward and away from the seal plate. A plurality of compressionsprings bias the seal face of carbon ring seal axially into a sealingrelationship with the seal face of the seal plate. The carbon ring sealhas an annularly-shaped exterior face disposed generally opposite theseal face of the carbon ring seal, and includes a plurality of axiallyextending circumferentially spaced apart apertures receiving therein thesecond ends of the pins to facilitate sliding axial alignment betweenthe carbon ring seal and the seal housing and to reduce the mass of thecarbon ring seal for improved dynamic alignment between the seal facesof the carbon ring seal and the seal plate.

Yet another aspect of the present invention is a gas seal for aerospaceengines and the like, which includes a low friction secondary seal forimproved seal integrity, without excess wear.

Yet another aspect of the present invention is a non-contact, lift offtype gas seal which meets the exacting dimensional, weight, stress andthermal demands experienced in high speed aircraft gas turbine enginesand similar turbo machinery.

Yet another aspect of the present invention is a gas seal for aerospaceengines and the like, which has an uncomplicated design, is efficient inuse, economical to manufacture, capable of a long operating life, andparticularly well adapted for the proposed use.

These and other advantages of the invention will be further understoodand appreciated by those skilled in the art by reference to thefollowing written specification, claims and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a gas seal embodying the presentinvention, taken from a front or interior side thereof.

FIG. 2 is a perspective view of the gas seal, taken from a back orexterior side thereof.

FIG. 3 is an exploded perspective view of the gas seal, shown with anassociated engine drive shaft and engine bearing.

FIG. 4 is an enlarged fragmentary perspective view of the gas seal.

FIG. 5 is a fragmentary perspective view of a stationary seal housingportion of the gas seal.

FIG. 6 is a fragmentary front elevational view of the stationary sealhousing.

FIG. 7 is a cross-sectional view of the stationary seal housing.

FIG. 8 is a fragmentary rear elevational view of the stationary sealhousing.

FIG. 9 is an enlarged plan view of a bayonet lock portion of thestationary seal housing.

FIG. 10 is a perspective view of a carbon ring seal portion of the gasseal.

FIG. 11 is a fragmentary front elevational view of the carbon ring seal.

FIG. 12 is a cross-sectional view of the carbon ring seal.

FIG. 13 is a fragmentary rear elevational view of the carbon ring seal.

FIG. 14 is an enlarged elevational view of a bayonet lock portion of thecarbon ring seal.

FIG. 15 is an enlarged plan view of the bayonet lock portion of thecarbon ring seal.

FIG. 16 is a perspective view of a locking plate portion of the gasseal.

FIG. 17 is a fragmentary front elevational view of the locking plate.

FIG. 18 is a cross-sectional view of the locking plate.

FIG. 19 is a fragmentary rear elevational view of the locking plate.

FIG. 20 is an enlarged fragmentary cross-sectional view of a marginalportion of the locking plate with a keyway and associated key shown in adisassembled condition.

FIG. 21 is an enlarged fragmentary view of the marginal portion of thelocking plate with the key shown assembled in the keyway.

FIG. 22 is a perspective view of the key shown in FIGS. 20 and 21.

FIG. 23 is a perspective view of a rotating seal plate portion of thegas seal.

FIG. 24 is a fragmentary front elevational view of the seal plate.

FIG. 25 is a cross-sectional view of the seal plate.

FIG. 26 is a fragmentary rear elevational view of the seal plate.

FIG. 27 is an enlarged fragmentary view of the seal plate showing akeyway portion thereof.

FIG. 28 is a perspective, cross-sectional view of the seal plate takenalong the line XXVIII-XXVIII, FIG. 27 showing the keyway portionthereof.

FIG. 29 is an enlarged fragmentary view of the seal plate, shown in adisassembled condition on the locking plate.

FIG. 30 is a perspective, cross-sectional view of the seal plate showninstalled on the locking plate.

FIG. 31 is a perspective view of a pressure balance plate portion of thegas seal.

FIG. 32 is a fragmentary front elevational view of the pressure balanceplate.

FIG. 33 is a cross-sectional view of the pressure balance plate.

FIG. 34 is a fragmentary rear elevational view of the pressure balanceplate.

FIG. 35 is an enlarged fragmentary cross-sectional view of the gas seal,showing the locking plate, seal plate and pressure balance plate in anassembled condition.

FIG. 36 is a perspective view of a flexible spring pin and a compressionspring portion of the gas seal, shown in an assembled condition.

FIG. 37 is a rear end elevational view of the spring pin.

FIG. 38 is a cross-sectional view of the spring pin.

FIG. 39 is a front end view of the spring pin.

FIG. 40 is a rear end view of the compression spring.

FIG. 41 is a side elevational view of the compression spring.

FIG. 42 is a front end view of the compression spring.

FIG. 43 is an enlarged fragmentary, partially schematic cross-sectionalview of the spring pin and compression spring shown during assembly ofthe bayonet connection.

FIG. 44 is an enlarged fragmentary cross-sectional view of the springpin and compression spring shown in an assembled operating condition.

FIG. 45 is an exploded perspective view of the gas seal, showing thecarbon ring seal prior to assembly in the seal housing.

FIG. 46 is an exploded perspective view of the gas seal, showing thecarbon ring seal being assembled into the seal housing.

FIG. 47 is an enlarged fragmentary cross-sectional view of the gas seal,shown during operation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For purposes of description herein, the terms “upper”, “lower”, “right”,“left”, “rear”, “front”, “vertical”, “horizontal” and derivativesthereof shall relate to the invention as oriented in FIG. 1. However, itis to be understood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings, and described in thefollowing specification, are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristics relating to theembodiments disclosed herein are not to be considered as limiting,unless the claims expressly state otherwise.

The reference numeral 1 (FIGS. 1-3) generally designates a gas sealembodying the present invention, which is particularly adapted for usein conjunction with aerospace engines and the like of the type having anengine housing 2 with an engine drive shaft 3 rotatably mounted therein.Gas seal 1 has a stationary seal housing 4 configured for rigidconnection with engine housing 2. A rotating seal plate 5 is configuredfor operable connection with the engine drive shaft 3, rotates therewithrelative to seal housing 4 and has a seal face 6. A carbon ring seal 7is movably supported in seal housing 4 and includes a seal face 8 whichmates with the seal face 6 of seal plate 5 to create a gas seal betweenthe engine housing 2 and the engine drive shaft 3. A plurality offlexible spring pins 9 have first ends 10 supported on seal housing 4and second ends 11 slidingly connected with carbon ring seal 7 to permitthe carbon ring seal to selectively shift axially in seal housing 4toward and away from seal plate 5. A plurality of compression springs 12are supported on flexible spring pins 9 and bias the seal face 8 ofcarbon ring seal 7 axially into a sealing relationship with the sealface 6 of seal plate 5. A first twist lock member 13 is associated withseal housing 4 and a second twist lock member 14 is associated withcarbon ring seal 7 and is configured to mate with the first twist lockmember 13 associated with seal housing 4 to securely yet detachablyretain carbon ring seal 7 in seal housing 4. The second ends 11 offlexible spring pins 9 are laterally flexible relative to the first ends10 of flexible spring pins 9 and can resiliently deflect in a generallycircular fashion during mutual rotation of seal housing 4 and carbonring seal 7 to facilitate engagement and disengagement of the first andsecond twist lock members 13, 14.

Gas seal 1 is particularly adapted for use in conjunction with aerospaceengines and the like, and as best illustrated in FIG. 4, serves to forma rotating seal between a relatively high pressure, high temperatureportion of the engine, which is identified by the reference numeral 20on the left-hand side of FIG. 4, and a relatively low pressure, lowtemperature portion of the engine, which is identified by the referencenumeral 21 on the right-hand side of FIG. 4. Typically, the relativelylow pressure, low temperature portion 21 of the engine comprises abearing and oil compartment of the aerospace engine. Pressure isgenerated by a compressor in the front of the engine and a combustor inrear of the engine, which generate the turbine's mode of force, andconstitute the high pressure, high temperature area 20 of the engine.Relative low pressure, low temperature air contained in the bearingcompartment or low pressure area 21 of the engine preferably contains afine oil mist, which is used to lubricate the various bearing portionsof the aerospace engine, including the gas seal 1. Gas seal 1 is anon-contact or lift off type of gas seal, wherein a very small amount ofthe relatively high pressure, high temperature air in engine compartment2 migrates at a controlled rate into the bearing and oil compartment 21of the engine by passing radially outwardly between the seal face 6 ofseal plate 5 and the seal face 8 of carbon ring seal 7, as shown by thearrows 22 in FIGS. 4 and 47.

For purposes of description herein, that side of gas seal 1 facing thehigh pressure area 20 of the engine is referred to as the back, exteriorand/or outer side, and that side of gas seal 1 facing the low pressurearea 21 of the engine is referred to as the front, inner and/or interiorside.

In the example illustrated in FIG. 3, engine drive shaft 3 is at leastpartially supported by a bearing 25 located within the low pressure areaor compartment 21 of the engine, and gas seal 1 forms a rotating sealbetween the high pressure area 20 of the engine and the low pressurearea 21 of the engine in which bearing 25 is disposed. With reference toFIG. 3, the illustrated gas seal 1 has three basic rotating elements orparts, comprising a locking plate 30, seal plate 5 and a pressurebalance plate 31. Locking plate 30 is mounted on engine drive shaft 3and rotates therewith. Seal plate 5 is mounted on locking plate 30 andalso rotates with locking plate 30 and engine drive shaft 3. Pressurebalance plate 31 is also mounted on engine drive shaft 3 and rotatestherewith at a location axially adjacent to seal plate 5 for purposes tobe described in greater detail hereinafter. The illustrated gas seal 1has six basic non-rotating elements or parts, comprising carbon ringseal 7, a retainer ring 34, a cover plate 35, a secondary seal 36,compression springs 12, spring pins 9 and seal housing 4. Spring pins 9and compression springs 12, in conjunction with the pressure generatedin the gas path, as described in greater detail below, resiliently urgecarbon ring seal 7 axially toward seal plate 5 to ensure proper contactbetween seal faces 6 and 8.

With reference to FIGS. 5-9, the illustrated seal housing 4 has a rigid,one-piece construction with a generally annular shape, and includes amarginal mounting flange 40 with axially extending fastener apertures 41for rigidly attaching gas seal 1 to stationary engine housing 2. Sealhousing 4 also has a body portion 42 adapted to retain the non-rotatingelements 7, 9, 12 and 34-36 of gas seal 1. More specifically, the bodyportion 42 of seal housing 4 includes an axially outwardly extending hub43 having a rear wall 44 with a continuous circular slot 45 in theinterior side thereof in which the outer ends 10 of spring pins 9 arereceived and selectively retained, as explained in greater detail below.Hub 43 also includes an inwardly opening pocket 46 in which carbon ringseal 7 is slidably retained for axial motion toward and away from sealplate 5. Hub 43 also defines a radially extending space or gaspassageway 47 between inner edge 50 and the rearward face 64 of carbonring seal 7, which communicates the high pressure, high temperature gasin engine compartment 20 with the rear or exterior side 64 of carbonring seal 7, as noted by the arrow 136 in FIGS. 4 and 47. Hub 43 alsoincludes an annularly-shaped axially oriented slot 48 in which secondaryseal 36 is retained by cover plate 35, as well as a radially orientedretainer slot 49 in which retaining ring 34 is received to hold coverplate 35 and secondary seal 36 in place. Seal housing 4 also includes aplurality of axially inwardly extending bayonet fingers or prongs 52which are disposed on the radially inward side of seal housing 4. Asbest illustrated in FIG. 9, each of the bayonet prongs 52 has ahook-shaped plan configuration, comprising a base portion 53, a straightedge portion 54, an arcuate edge portion 55 disposed opposite edge 54and an L-shaped hook portion 56 having a circumferentially extendingtooth 57 which defines a seal support ledge 58. In the illustratedexample, seal housing 4 has eight substantially identical bayonet prongs52, which are spaced generally equidistantly around the innercircumference of seal housing 4 and serve to detachably mount carbonring seal 7 thereto in the manner described in greater detailhereinbelow.

With reference to FIGS. 10-15, the illustrated carbon ring seal 7 has aone-piece, monolithic construction, with a generally annular shapehaving seal face 8 disposed on the inner side thereof and an outer face64 disposed opposite seal face 8. In the illustrated example, seal face8 includes a plurality of circumferentially spaced apart ramps 65 whichserve to create a thin, hydrodynamic gas film between the seal face 8 ofcarbon ring seal 7 and the seal face 6 of seal plate 5 when engine driveshaft 3 is rotating during engine operation. The outer face 64 of carbonring seal 7 includes a plurality of axially extending, blind apertures66 spaced equidistantly about a central area thereof, which are shapedto receive and retain therein spring pins 9, along with compressionsprings 12 mounted on spring pins 9. As discussed in greater detailbelow, blind apertures 66 serve to both retain spring pins 9 andcompression springs 12 in proper axial alignment with carbon ring seal 7and seal housing 4, and also reduce the mass of carbon ring seal 7 forimproved dynamic alignment between seal faces 6 and 8. The exteriormarginal surface of carbon ring seal 7 has a collar 67, with seal face 8protruding radially outwardly to create a notch or shoulder area 69 witha cylindrical base surface 70 against which secondary seal 36 abuts.Preferably, base surface 70 has a low friction coating thereon whichfacilitates axial motion of carbon ring seal 7 relative to secondaryseal 36, while maintaining a secure gas seal between the abuttingsurfaces. The inner marginal surface 71 of carbon ring seal 7 includes aplurality of radially inwardly protruding bayonet tabs 72, which aregenerally flush or planar with outer face 64, and selectively engage thebayonet prongs 52 on seal housing 4, as described in greater detailbelow. In the illustrated example, bayonet tabs 72 have a tapered ortrapezoidal side elevational configuration, and include flat oppositeside faces 73 and 74, angled side edges 75 and an arcuate marginal edge76. The illustrated carbon ring seal 7 has a one-piece, integralconstruction made from carbon or graphite, such that it is relativelylight-weight, and forms a flat compliant seal face 8 for sealingengagement with the more rigid seal face 6 of seal plate 5. As is wellknown in the art, various areas of carbon ring seal 7 wear duringoperation, including seal face 8, outer surface 70, tabs 72, etc., suchthat carbon ring seal 7 must be replaced on a regular basis to ensureproper operation.

With reference to FIGS. 16-22, the illustrated locking plate 30 has arigid, one-piece construction with a generally annular shape, includingcylindrically-shaped outer and inner marginal surfaces 80 and 81, aswell as opposite side faces 82 and 83. The inner marginal surface 81 oflocking plate 30 is shaped to be closely received over engine driveshaft 3 and rotatably attached thereto by a locknut or the like (notshown), such that locking plate 30 rotates with engine drive shaft 3.The outer marginal surface 80 of locking plate 30 includes a radiallyoutwardly protruding rim 84 which defines a shoulder 85 adjacent sideface 82 on which seal plate 5 is supported in the manner described ingreater detail hereinbelow. As best illustrated in FIGS. 16, 20 and 21,shoulder 85 includes a plurality of radially inwardly extending keyways86 spaced generally equidistantly about outer shoulder 85 in whichassociated keys 87 are received. In the illustrated example, keyways 86have a substantially identical configuration, with a rectangular planshape that that is elongated in the direction of the circumference ofouter marginal surface 80. With reference to FIGS. 20-22, theillustrated keys 87 have a shape similar to that of keyways 86,comprising radially inner and outer edges 88 and 89, as well as oppositeside edges 90. In the illustrated example, side edges 90 are generallytapered, and outer edge 89 has a slightly arcuate shape which protrudesradially outwardly from shoulder 85, as shown in FIG. 21.

With reference to FIGS. 23-30, the illustrated seal plate 5 is anaxially floating seal plate, and has a rigid, one-piece constructionwith a generally annular shape comprising a circular outer marginal edgeor surface 95, a circular inner marginal edge or surface 96 and oppositeside faces 6 and 97. The inner marginal edge 96 of seal plate 5 includesa plurality of circumferentially spaced apart keyways 99 which areoriented for radial alignment with the keyways 86 in locking plate 30and are shaped to receive therein the radially outward portions of keys87, as shown in FIGS. 29 and 30, so as to rotatably lock seal plate 5onto locking plate 30, such that locking plate 30 and seal plate 5rotate with engine drive shaft 3. In the illustrated example, keyways 99are in the form of open sided, generally rectangular notches such thatseal plate 5 can float or shift selectively in an axial direction towardand away from carbon ring seal 7, as shown in FIG. 30, and described ingreater detail hereinafter. The rim 84 of locking plate 30 abuts theradially inward portion of the seal face 6 of seal plate 5 to positivelylimit the axially outwardly shifting movement of seal plate 5. Theopposite faces 6 and 97 of seal plate 5 are substantially flat andmutually parallel. Preferably, seal plate 5 is constructed from metal,such as steel or the like.

With reference to FIGS. 31-35, the illustrated pressure balance plate 31has a rigid, one-piece construction with a generally annular shape,comprising a circular outer marginal edge or surface 104, a circularinner marginal edge or surface 105 and opposite side faces 106 and 107.Side faces 106 and 107 are generally flat and mutually parallel. As bestillustrated in FIGS. 32-34, side face 106 includes two annularly-shapedrecesses 108 and 109 disposed concentrically relative to inner marginaledge 105, and side face 107 includes an outwardly protruding shoulder110 disposed adjacent inner marginal edge 105. The outer side face 106also includes an annularly-shaped groove 111 that forms part of apassageway through which pressurized air from engine compartment 2 isapplied to the interior face 97 of floating seal plate 5 to resilientlyurge floating seal plate 5 toward carbon ring seal 7 and balance thepressure applied to seal plate 5 by carbon ring seal 7. The innermarginal edge 105 of pressure balance plate 31 is adapted to be closelyreceived over engine drive shaft 3 and rotatably connected thereto, suchthat pressure balance plate 31, locking plate 30 and floating seal plate5 all rotate with engine drive shaft 3, but permit seal plate 5 to shiftselectively axially toward and away from carbon ring seal 7. As bestillustrated in FIG. 35, the innermost portion of the shoulder 85 onlocking plate 30, along with locking ring face 82, are received in theannular recess 108 in pressure balance plate 31 and positively centerthe same in an axially aligned relationship.

With reference to FIGS. 36-42, the illustrated spring pins 9 have anintegral or one-piece construction made from a high temperature polymeror the like, such that they are resiliently flexible in a lateral orside-to-side direction, like a leaf spring. Each of the spring pins 9has a substantially identical construction, such that reference hereinshall be made to the spring pin illustrated in FIG. 36, with it beingunderstood that the remaining spring pins 9 are substantially identical.As best illustrated in FIGS. 36-39, the outer or first end 10 of springpin 9 is in the form of an enlarged head having a circular endelevational shape. The body of spring pin 9 comprises acylindrically-shaped shank 118 which has a central aperture 119 formedtherethrough. The interior or second end 11 of spring pin 9 has atapered configuration which facilitates insertion into an associatedcompression spring 12, as well as an associated one of the apertures 66formed in the exterior face of carbon ring seal 7. The enlarged head end10 of spring pin 9 is received and rides in the annular groove or slot45 in seal housing 4, so as to retain the same in an axially extendingorientation, but permit selected circumferential movement of spring pin9 for purposes to be described in greater detail hereinafter.

With reference to FIGS. 36 and 40-42, the illustrated compressionsprings 12 have a substantially identical construction, and eachcomprises a wound coil spring having an interior aperture 123 shaped tobe closely received over the shank 118 of an associated spring pin 9.The outer end 124 of coil spring 12 abuts the enlarged head end 10 ofspring pin 9, as shown in FIG. 36, while the inner end 125 ofcompression spring 12 is received within an associated aperture 66 incarbon ring seal 7 and abuts the interior end of the same. Consequently,coil springs 12 serve to bias carbon ring seal 7 axially outwardlytoward seal plate 5.

With reference to FIGS. 45 and 46, the rotating elements 5, 30 and 31 ofgas seal 1 are assembled in the following fashion. Locking plate 30 isinserted over the outer surface of engine drive shaft 3 and is receivedclosely thereon. Seal plate 5 is then mounted on the shoulder 85 oflocking plate 30, with keys 87 inserted into the opposite keyways 86 and99, as shown in FIGS. 29 and 30, so as to rotatably couple engine driveshaft 3, seal plate 5 and locking plate 30, yet permit seal plate 5 toshift selectively axially on shoulder 85. Pressure balance plate 31 isthen mounted on engine drive shaft 3 with the outer side face 106abutting the inner face 97 of seal plate 5. Bearing 25 (FIG. 3) ismounted on engine drive shaft 3 and retained axially in place by a shaftshoulder and/or locking nut (not shown), so as to retain locking plate30, seal plate 5 and pressure balance plate 31 in an axially formedstack which rotates with engine drive shaft 3. In one embodiment of thepresent invention, the rotating elements 5, 30 and 31 of gas seal 1 areheld in place on the rotating engine drive shaft 3 by an axialcompression load typically applied between a locknut (not shown) and theinner race of bearing 25.

The non-rotating or stationary elements 7, 9, 12 and 34-36 of gas seal 1are assembled in the following fashion. Seal housing 4 is attached tothe engine housing 2 using a plurality of threaded fasteners 130 (FIGS.45 and 46) inserted through the apertures 41 in the marginal mountingflange 40 of seal housing 4. A plurality of compression springs 12 aremounted in the apertures 66 in the outer face 64 of carbon ring seal 7,and a plurality of spring pins 9 are inserted into the hollow interiors123 of compression springs 12. Secondary seal 36 is then assembled overthe exterior marginal surface 70 of carbon ring seal 7, along with coverplate 35. With spring pins 9 and compression springs 12 assembled incarbon ring seal 7, the outer face 64 of carbon ring seal 7 is insertedinto the annular opening or pocket 46 in the hub portion 43 of sealhousing 4. As discussed above, the enlarged head ends 10 of spring pins9 are received and ride in the annular groove or slot 45 in the interiorof seal housing 4 which radially locates spring pins 9 and compressionsprings 12, but permits the same to selectively shift circumferentiallyrelative to seal housing 4. The bayonet tabs 72 on carbon ring seal 7are positioned in between the bayonet prongs 52 on seal housing 4, asshown in FIG. 46, and carbon ring seal 7 is then shifted axiallyinwardly toward seal housing 4, thereby compressing compression springs12, until such time as the inner sides or faces 74 of bayonet tabs 72clear the interior ledges 58 of bayonet prongs 52. Carbon ring seal 7 isthen rotated slightly in a clockwise or counterclockwise direction,depending upon the direction of rotation of engine drive shaft 3, untilsuch time as the hook portions 56 of bayonet prongs 52 on seal housing 4engage the side edges 75 of the bayonet tabs 72 on carbon ring seal 7.As best shown in FIG. 44, compression springs 12 bias the inner sides orfaces 74 of bayonet tabs 72 securely against the interior ledges 58 ofbayonet prongs 52 to axially position the same in an arcuate, butnon-rigid relationship. Carbon ring seal 7 is thereby securely retainedin place in seal housing 4 in a manner which permits carbon ring seal 7to shift selectively axially toward and away from seal plate 5 duringengine operation, and to be easily removed and replaced as necessary.

With reference to FIGS. 43 and 44, the configuration of spring pins 9and compression springs 12 facilitates engagement and disengagement ofthe bayonet connectors 52 and 72 on seal housing 4 and carbon ring seal7, and also serves to self-compensate for any wear in the contactportions of gas seal 1, as well as any slight misalignment that mightoccur between seal faces 6 and 8, particularly during high torque andhigh speed engine conditions. More specifically, the lateral flexibilityof spring pins 9, which is shown in a somewhat exaggerated manner inFIG. 43, permits the inward ends 11 to shift resiliently in a circularfashion relative to the enlarged head ends 10, while maintaining thecolumnar or generally cylindrical shape of both spring pins 9 andcompression springs 12. Also, the enlarge head ends 10 of spring pins 9can shift in a circular pattern within the retaining slot or groove 45in seal housing 4, which not only facilitates rotation of carbon ringseal 7 relative to seal housing 4 to engage and disengage bayonetconnections 52 and 72, but also self-compensates as the anti-rotationfeatures on carbon ring seal 7 wear. The bayonet tabs 72 on carbon ringseal 7 also wear from the constant circumferential torque and axialfretting motion between carbon ring seal 7 and seal housing bayonetprongs 52, as shown in FIG. 44. This wear will cause a normally small,but potentially significant rotation of carbon ring seal 7 relative toseal housing 4. Spring pins 9 provide axial spring alignment for boththe assembly of bayonet connectors 52 and 72, and the compensation forwear on carbon ring seal 7, particularly tabs 72.

When the aerospace engine is in operation, gas seal 1 functions in thefollowing manner. With reference to FIGS. 4 and 47, a very small amountof the relatively high pressure, high temperature air in compartment orarea 20 of the engine migrates at a controlled rate from compartment 20to the bearing and oil compartment 21 of the engine by passing radiallyoutwardly between the annularly-shaped faces 6, 8 of seal plate 5 andcarbon ring seal 7, respectively, as shown by the arrows 22. Therotation of seal plate 5 relative to carbon ring seal 7 creates ahydrodynamic film which causes the seal faces 6 and 8 to lift off oneanother or separate slightly, so that they do not physically touch orabut during normal operation, so as to ensure a long operating life. Theradially extending channel 47 formed between seal housing hub 43 and theouter face 64 of carbon ring seal 7 defines the air gap or passagewaynoted by the arrow 136 through which the relative high pressure, hightemperature air in engine compartment 20 is communicated with the outerend face 64 of carbon ring seal 7, and thereby urges the seal face 8 ofcarbon ring seal 7 outwardly toward seal face 6 of floating seal plate5. The low friction carbon secondary seal 36 mounted in seal housing 4seals against the radially outermost surface 70 of carbon ring seal 7 toensure that the relatively high pressure, high temperature air in thegas path compartment 20 does not flow unchecked into the engine bearingcompartment 21.

A unique aspect of gas seal 1 is the construction of and dynamicinterface between floating seal plate 5 and pressure balance plate 31.More specifically, in conventional gas seals, the rotating seal plate istypically fixedly clamped in an axial stack on an associated shaft, andthe carbon ring is urged resiliently axially into abutment with therotating seal plate by springs or the like. This direct clamping in thestack can experience distortion from high stack loads. In the presentaerospace engine environment, the high pressure gases in enginecompartment 20 act on carbon ring seal 7, and create substantial forces,which urge the same axially outwardly with sufficient force against sealplate 5 that they can also tend to distort the flat shape of the sealplate face 6 and/or the carbon ring seal face 8, thereby adverselyimpacting the integrity of the seal. In the present gas seal 1, sealplate 5 is permitted to shift or float axially relative to locking plate30 and pressure balance plate 31, so as to avoid these sources ofdistortion. Also, the adjacent surfaces 106 and 97, and 96 and 85 ofpressure balance plate 31, floating seal plate 5 and locking plate 30are configured to create a passageway along the radially inward edge offloating seal plate 5 for the high pressure, high temperature gases inengine compartment 20 to pass to the groove 111 in pressure balanceplate 31, as shown by the arrows 137 in FIGS. 4 and 47. As discussedabove, this gas pressure serves to urge floating seal plate 5 axiallyoutwardly toward carbon ring seal 7, and counterbalances the axialinward forces created by the high pressure gases in engine compartment20 acting on the seal face 6 of seal plate 5 through carbon ring seal 7.The axially floating nature of seal plate 5 along with thecounterbalancing pressure applied by pressure balance plate 31 ensurethat seal plate 5 will not warp or distort even when the pressures inengine compartment 20 are very high.

In the foregoing description, it will be readily appreciated by thoseskilled in the art that modifications may be made to the inventionwithout departing from the concepts disclosed herein. Such modificationsare to be considered as included in the following claims, unless theseclaims by their language expressly state otherwise.

The invention claimed is:
 1. A gas seal for aerospace engines and the like of the type having an engine housing with an engine drive shaft rotatably mounted therein, comprising: a stationary seal housing configured for rigid connection with the engine housing; a rotating seal plate that is configured for operable connection with the engine drive shaft, and rotates therewith relative to said seal housing and has a seal face; a carbon ring seal movably supported in said seal housing and including a seal face which mates with said seal face of said seal plate to create a gas seal between the engine housing and the engine drive shaft; a plurality of pins having first ends thereof movably supported on said seal housing and second ends thereof slidingly connected with said carbon ring seal to permit said carbon ring seal to selectively shift axially in said seal housing toward and away from said seal plate and to permit rotational movement of said carbon ring seal relative to said stationary seal housing; a plurality of compression springs biasing said seal face of said carbon ring seal axially into a sealing relationship with said seal face of said seal plate; and wherein said carbon ring seal has an annularly-shaped exterior face disposed generally opposite said seal face of said carbon ring seal, and includes a plurality of axially extending circumferentially spaced apart apertures receiving therein said second ends of said pins to facilitate sliding axial alignment between said carbon ring seal and said seal housing, and to reduce the mass of said carbon ring seal for improved dynamic alignment between said seal faces of said carbon ring seal and said seal plate.
 2. A gas seal as set forth in claim 1, wherein: said compression springs comprise coil springs which are retained coaxially on said pins, and are received in said apertures in said exterior face of said carbon ring seal.
 3. A gas seal as set forth in claim 2, including: a first twist lock member associated with said seal housing: a second twist lock member associated with said carbon ring seal and configured to mate with said first twist lock member associated with said seal housing to securely yet detachably retain said carbon ring seal in said seal housing; and wherein said pins comprise flexible spring pins having first and second ends, and wherein said second ends of said flexible spring pins are laterally flexible relative to said first ends of said flexible spring pins and can resiliently deflect in a generally circular fashion during mutual rotation of said seal housing and said carbon ring seal to facilitate engagement and disengagement of said first and second twist lock members.
 4. A gas seal as set forth in claim 1, wherein: said pins have a generally columnar shape, and are constructed from a high temperature polymer to facilitate selected resilient lateral flexure.
 5. A gas seal as set forth in claim 4, wherein: said first and second twist lock members define a bayonet coupling wherein said carbon ring seal is axially converged and rotated relative to said seal housing into a locked position.
 6. A gas seal as set forth in claim 5, wherein: said seal housing includes an annularly-shaped groove in which said first ends of said spring pins are received and retained.
 7. A gas seal as set forth in claim 6, wherein: said spring pins have a generally cylindrical shape with enlarged heads at said first ends thereof against which the associated outer ends of said compression springs abut, and which are closely received in said groove in said seal housing to permit circumferential shifting therebetween to automatically compensate for wear in said carbon ring seal.
 8. A gas seal as set forth in claim 1, including: a first twist lock member associated with said seal housing: a second twist lock member associated with said carbon ring seal and configured to mate with said first twist lock member associated with said seal housing to securely yet detachably retain said carbon ring seal in said seal housing; and wherein said pins comprise flexible spring pins having first and second ends, and wherein said second ends of said flexible spring pins are laterally flexible relative to said first ends of said flexible spring pins and can resiliently deflect in a generally circular fashion during mutual rotation of said seal housing and said carbon ring seal to facilitate engagement and disengagement of said first and second twist lock members.
 9. A gas seal as set forth in claim 1, wherein: said compression pins have a generally columnar shape, and are constructed from a high temperature polymer to facilitate selected resilient lateral flexure.
 10. A gas seal as set forth in claim 8, wherein: said first and second twist lock members define a bayonet coupling wherein said carbon ring seal is axially converged and rotated relative to said seal housing into a locked position.
 11. A gas seal as set forth in claim 1, wherein: said seal housing includes an annularly-shaped groove in which said first ends of said pins are received and retained.
 12. A gas seal as set forth in claim 11, wherein: said pins have a generally cylindrical shape with enlarged heads at said first ends thereof against which the associated outer ends of said compression springs abut, and which are closely received in said groove in said seal housing to permit circumferential shifting therebetween to automatically compensate for wear in said carbon ring seal.
 13. A gas seal for aerospace engines and the like of the type having an engine housing with an engine drive shaft rotatably mounted therein, comprising: a carbon ring seal; a stationary seal housing configured for rigid connection with the engine housing; an axially floating seal plate configured for operable connection with the engine drive shaft and rotates therewith relative to said seal housing and floats in an axial direction toward and away from said carbon ring seal, the seal plate having a seal face; wherein the carbon ring seal is movably supported in said seal housing and includes a seal face which mates with said seal face of said seal plate to create a gas seal between the engine housing and the engine drive shaft; a plurality of pins having first ends thereof movably supported on said seal housing and second ends thereof slidingly connected with said carbon ring seal to permit said carbon ring seal to selectively shift axially in said seal housing toward and away from said seal plate and to permit rotational movement of said carbon ring seal relative to said stationary seal housing; a plurality of compression springs biasing said seal face of said carbon ring seal axially into a sealing relationship with said seal face of said seal plate; and wherein said carbon ring seal has an annularly-shaped exterior face disposed generally opposite said seal face of said carbon ring seal, and includes a plurality of axially extending circumferentially spaced apart apertures receiving therein said second ends of said pins to facilitate sliding axial alignment between said carbon ring seal and said seal housing, and to reduce the mass of said carbon ring seal for improved dynamic alignment between said seal faces of said carbon ring seal and said seal plate.
 14. A gas seal as set forth in claim 13, wherein: said compression springs comprise coil springs which are retained coaxially on said pins, and are received in said apertures in said exterior face of said carbon ring seal.
 15. A gas seal as set forth in claim 13, wherein: said pins have a generally columnar shape, and are constructed from a high temperature polymer to facilitate selected resilient lateral flexure.
 16. An aerospace engine, comprising: an engine housing; an engine drive shaft rotatably mounted in the housing; a high pressure area formed by a compressor and a combustor; a low pressure area formed by a bearing compartment; a gas seal configured to seal the high pressure area from the low pressure area, the gas seal comprising: a stationary seal housing configured for rigid connection with the engine housing; a rotating seal plate that is configured for operable connection with the engine drive shaft and rotates therewith relative to said seal housing and has a seal face; a carbon ring seal movably supported in said seal housing and including a seal face which mates with said seal face of said seal plate to create a gas seal between the engine housing and the engine drive shaft; a plurality of pins having first ends thereof movably supported on said seal housing and second ends thereof slidingly connected with said carbon ring seal to permit said carbon ring seal to selectively shift axially in said seal housing toward and away from said seal plate and to permit rotational movement of said carbon ring seal relative to said stationary seal housing; a plurality of compression springs biasing said seal face of said carbon ring seal axially into a sealing relationship with said seal face of said seal plate; and wherein said carbon ring seal has an annularly-shaped exterior face disposed generally opposite said seal face of said carbon ring seal, and includes a plurality of axially extending circumferentially spaced apart apertures receiving therein said second ends of said pins to facilitate sliding axial alignment between said carbon ring seal and said seal housing, and to reduce the mass of said carbon ring seal for improved dynamic alignment between said seal faces of said carbon ring seal and said seal plate.
 17. The aerospace engine of claim 16, wherein: the seal face includes a plurality of circumferentially spaced apart ramps that create a hydrodynamic gas film between the seal face of the carbon ring seal and the seal face of the seal plate.
 18. An aerospace engine as set forth in claim 16, wherein: said compression springs comprise coil springs which are retained coaxially on said pins, and are received in said apertures in said exterior face of said carbon ring seal. 